Traditional airplane interior lighting systems typically use fluorescent lamps. This technology currently provides the best efficiency available, requiring less electrical power, and producing less heat than other methods. However, fluorescent lamps can have a significant variance in brightness and color, and these properties can change with age. This can be quite noticeable in a system with multiple fluorescent lamps, and can detract from an interior design. Additionally, control of fluorescent lamps is limited. Typical installations will have three modes: off, bright, and dim, without any smooth transitions between. Continuously dimmable systems are available, but with a significant cost and weight penalty, and such systems still cannot be dimmed smoothly to and from an off condition.
Dynamic LED lighting systems (as used, for example, on the Boeing 787 aircraft) utilize multi-color LED elements to allow finely variable brightness and to introduce color-changing capabilities. Additionally, most dynamic LED systems include a calibration feature to ensure consistency across the installation. Calibration may be performed during manufacturing, or the system may include self-sensing to perform automatic and continuous calibration during operation.
The primary drawback to this type of dynamic LED lighting system is that the LEDs currently in use are not particularly energy-efficient when the design goal is to create large amounts of white light. Use of dynamic LED lighting systems increases power demands and waste heat, which in turn increases weight in the electrical power generation, distribution, light housings, heat sinks, and cooling systems, in comparison to a purely fluorescent-based system.
Previous consideration has been made to using a hybrid system that uses both LEDs and fluorescent lights. Typically, when full brightness is needed, white light is also desired. The fluorescent lights are utilized to improve efficiency during peak demand times. The LED elements are used for lower brightness levels, when the inefficiency is less of an issue, and when the full spectrum color variability would be used to provide enhanced mood lighting not possible with the fluorescent lamps. In effect, they operate as if they were two separate systems that are installed side-by-side, and current designs are not taking the full benefit of using them together.
A hybrid system has not been implemented, primarily because the “bright” fluorescent mode still exhibits all the consistency problems of a traditional fluorescent system. LED systems were introduced as a means to solve these problems as well as provide highly distinguishing mood lighting. Their combination together in the currently available hybrid designs has never attracted much interest, however, because such current designs seem to have the worst of all problems associated with both technologies.
It is therefore desirable to take a new approach of marrying the technologies together as if they were a single light source to allow for an improved hybrid design that takes advantage of the strengths of both technologies, rather than to follow the traditional method of operating both technologies as stand alone items that just happen to share the same enclosure.